ah right. and i wrote 'faithful copy' which it isn't; it's just that i read some manufacturer thing where they said they'd copied it. evidently not so, then.

saw the filter looked like a diode ladder, hence the question.

it isn't a bad little unit at all-and maybe the filter could be improved in this way. seem to remember it didn't quite get there, and the overall sound was a bit harsh.

not necessarily to make it 'pure 303', but maybe give it a bit more range using some of the tricks used here, if there are any 'obvious' weak points.other points:there are a couple of mods to FM and resonance online; and i've wondered about trying to get longer keyed notes(the decay is set and cuts off)..i mean, i have a x0x now, so i thought something slightly different and complementary.it has a sub osc, and pulse/saw can be mixed, and there's-i think- PWM.

the filter section looks very familiar. but i really don't have the experience/skills/knowledge at this stage, and ask out of curiosity. it's a decent little unit that could do more, has midi cc control, etc. thinking it could be expanded to be something other than a 303? has sub-osc, pwm..

there might be more info somewhere, parts, etc. thanks for any time, info, interest, etc.

While the filter is a fairly accurate copy electronically, it is built with CA3046 chips and only a few discrete transistors. It's a decent design, and switching C2291 and C1583 in place of the CA3046 chips is not only likely to make no audible difference. However it is highly likely to drive the experimenter INSANE trying to fit the individual transistors in the holes correctly, especially trying to figure out which four holes will be left empty.

Put it this way, yes, I could do it, but I wouldn't. I don't have so much hair left on the very top of my head that the amount I'd pull out in the process wouldn't show... ...especially since it will sound the same after all that work.

Don Taylor, a.k.a. Brassteacher"Jack of all trades, master of none, proficient at even fewer..."

haw haw..so you're saying the CA3046's replace transistors, and it'd be a major pain to transfer/replace these within same location?so, getting somewhere, anyway. thanks for having a look.

altitude, i have better copies if these weren't good, i'll dig them out.(may be more infos there too)

not quitting on this yet, though :) since this thing does deserve some thought, i reckon: it's still a pretty good little monosynth, and it's analogue, and has potential for mods, whatever they could be.(for the sake of argument...)

x0x mods are very specific, seeking to emulate a specific device exactly.this doesn't have to be about that. (you can mash out perfectly good acid with an ms10, really. bit darker though...)

ok: so i thought it might be fun to be able to oct/detune the osc+sub, that it might be fun to add an lfo to modulate pwm(?), and that something could be done about the eg decay on notes (currently it can't hold a note longer than preset decay if playing it keyed-eg: no sustain). i also remember not being totally happy with the slide action, so i don't know if it resembles 303/x0x. (you have to do the overlapping notes thing).

other than that, the filter lacked something. sorry, i know it's a long wishlist, but that's the cat out of the bag anyway. cheerz.

human fly wrote:haw haw..so you're saying the CA3046's replace transistors, and it'd be a major pain to transfer/replace these within same location?so, getting somewhere, anyway. thanks for having a look.

other than that, the filter lacked something. sorry, i know it's a long wishlist, but that's the cat out of the bag anyway. cheerz.

Now, given you've said above, changing the filter to be a TB-303 filter would be a pain. However, changing it into a Moog transistor ladder filter would be EASY. The board layout would be nearly identical, as most later Moog factory filter builds used CA3046 for the top and the bottom of the ladder.

If you want to try it, let me know, and I'll write up a set of instructions.

Don Taylor, a.k.a. Brassteacher"Jack of all trades, master of none, proficient at even fewer..."

so, it looks like transistors are replaced by ca3046 ic's?(is this anything to do with midi cc control?)

No, mostly economy, one chip replaces 5 transistors, and they happen to be pretty well matched, plus one pair is connected as a differential amp already.

human fly wrote:@brassteacher: could the moog mod be switchable, to keep orig 18dB/oct filter? there's a 'res' boost' mod for it that allows filter to self oscillate; is this the same?

No, the only way to do that would be to build the Moog filter on a daughter card and put a switch between the two. A properly built and calibrated Moog filter can indeed self oscillate, not sure what to do for the original filter, I haven't looked at the schematics yet.

human fly wrote:i read that this unit is 'poorly manufactured' and that solder pads are prones to lifting, it's fragile etc.

Even "well manufactured" boards are prone to solder pads lifting, especially if they are double-sided with through-plated holes. Those take longer to heat enough to melt solder. It's safer to use solder wick on a double-sided board, and I use a solder-sucker on single-sided ones.

Don Taylor, a.k.a. Brassteacher"Jack of all trades, master of none, proficient at even fewer..."